This invention is in the field of photoflash lamp units, such as multiple flash arrays having flash lamps enclosed in a housing provided with a transparent front cover through which light passes from a lamp when flashed.
Various reflector designs have been devised to direct the light from a flashing lamp toward the scene being photographed, so as to utilize the light more effectively than would be the case with a bare lamp emitting its light in all directions. Concave reflectors are customarily positioned behind the flash lamps so as to reflect and concentrate the light of the flashing lamp toward the scene being photographed. For example, U.S. Pat. No. 3,609,332 to Donald R. Schindler discloses a flash lamp unit having elongated concave quasi-cylindrical reflectors positioned behind and axially aligned with elongated tubular flash lamps. These reflectors, the side portions of which extend laterally sideways of and flank the lamps, have a parabolic curvature so as to effectively reflect a maximum of light from a flashing lamp in a frontward direction to illuminate the scene being photographed. U.S. Pat. No. 3,993,896 to Alfred Wacker discloses a flash lamp unit having elongated concave quasi-cylindrical reflectors of which the side portions which extend laterally sideways of and flank the lamps are flat instead of having parabolic curvatures as in the Schindler patent, and therefore reflect light more laterally than required to illuminate the scene to be photographed, whereby some of the light would be wasted. To usefully recover some of this reflected light that would be wasted, the transparent front cover is provided with groups of prisms in front of the side portions of the reflectors, which prisms direct the reflected light more frontwardly toward the scene to be photographed. German Pat. No. V6678 discloses a somewhat similar reflector-prism arrangement, in combination with a gas discharge tube. U.S. Pat. No. 3,878,385 to Kingston discloses a flash cover provided with concentric circular prisms for concentrating light when the lamp is flashed.